1. Field of Invention
The present invention relates in general to transmissions of motor vehicles, and more particularly to toroidal type continuously variable transmissions of wheeled motor vehicles.
2. Description of Related Art
Hitherto, various toroidal type continuously variable transmissions have been proposed and put into practical use in the field of motor vehicles, for the easiness with which the motor vehicle having such transmission mounted thereon can be driven and handled.
Usually, to constantly keep operative contact between each of input and output discs and each of paired power rollers, the transmissions of such type are equipped with a loading cam device by which the distance between the input and output discs is adjusted in accordance with inclination of the power rollers. That is, the loading cam device functions to move the input disc axially relative to the output disc. However, since the pivot axis of the trunnion is an axis that is fixed, the operative contact of the power rollers to the input and output discs achieved by adjustment of the distance between the input and output discs by the loading cam device needs a movement of each power roller in a given direction perpendicular to both the rotation axis of the power roller and the trunnion pivot axis. Particularly, the movement of each power roller in such a given direction is needed when due to long usage, operation surfaces of such input and output discs have become deformed and/or when the input and output discs and the power rollers are subjected to a misalignment upon assembly.
Thus, in the transmissions of the above-mentioned type, a so-called xe2x80x9cpower roller supporting structurexe2x80x9d is employed by which the movement of each power roller in such direction is carried out.
One of the power roller supporting structures is shown in Laid-open Japanese Patent Application (Tokkaihei) 11-159590. In the structure of this publication, there is employed a pivot shaft which supports the power roller and the trunnion on mutually eccentric portions, so that pivot movement of the power roller permits movement of the same in such a given direction.
Another power roller supporting structure is shown in Laid-Open Japanese Patent Application (Tokkaihei) 7-198014. The supporting structure of this publication is constructed to eliminate or minimize undesired torque shift of transmission.
The power roller supporting structure of 7-198014 publication is schematically illustrated in FIG. 12 of the accompanying drawings. As shown, a power roller receiving recess 202 is formed in a trunnion 200, which extends along the common axis of input and output discs (not shown). Linear bearings 204a and 204b are each interposed between a power roller 206 in the recess 202 and an inner wall of the recess 202. With this construction, the power roller 206 can move in a given direction to effect a parallel displacement thereof. As shown, the power roller 206 comprises a power inner roller 208, a power roller bearing (ball bearing) 210, a power outer roller 212 and a shaft 214 integral with power outer roller 212. In this supporting structure, it tends to occur that under operation, power outer roller 212 is brought into contact with an inner side wall of power roller receiving recess 202 when a vertical load (viz., load applied in the direction of the trunnion pivot axis) is applied to the power roller 206. If such contact occurs, smoothed parallel displacement of power roller 206 may be sacrificed.
Considering the above, the applicants have thought out some ideas which are depicted by FIGS. 13 and 14 of the accompanying drawings.
FIG. 13 depicts an idea that may eliminate the weak point of the structure of the 7-198014 publication. As shown, two roller bearings 216 and 218 are each disposed between the inner side wall of power roller receiving recess 202 and power outer roller 212. Due to provision of roller bearings 216 and 218, smoothed parallel displacement of power roller 206 is achieved. Designated by numeral 200a is a pivot axis of the trunnion 200.
FIG. 14 depicts another idea. Also in this idea, two roller bearings 220 and 222 are each disposed between the inner wall of the power roller receiving recess 202 and power outer roller 212. However, as shown, in this idea, each roller bearing 220 or 222 is arranged between an inclined flat portion of the inner wall of the recess 202 and an inclined flat portion of power outer roller 212. Due to provision of such inclined roller bearings 220 and 222, a load in the direction of the rotation axis of power roller 206 as well as a load in the direction of the trunnion pivot axis are effectively supported by trunnion 200, and due to the same reason, smoothed parallel displacement of power roller 206 is achieved.
However, even the power roller supporting structures described hereinabove fail to satisfy manufacturers. That is, it is quite difficult to machine power outer roller 212 because of obstruction by shaft 214 that is integral with roller 212. In fact, due to such obstruction, producing an annular guide groove for power roller bearing (ball bearing) 210 needs a time-consumed and skilled machining technique, which increases the cost of the transmission.
Accordingly, an object of the present invention is to provide a toroidal type continuously variable transmission which is free of the above-mentioned weak points.
According to the present invention, there is provided a toroidal type continuously variable transmission which comprises a power outer roller and a shaft which are produced as separate members. The power outer roller is machined with an annular guide groove for a power roller bearing (ball bearing). Upon assembly, the shaft is coupled with the power outer roller. With this, economical production of power roller supporting structure is achieved while suppressing undesired inclination phenomenon of the shaft.
According to a first aspect of the present invention, there is provided a toroidal type continuously variable transmission which comprises input and output discs coaxially arranged; a pair of power rollers, each being operatively disposed between the input and output discs and including a power inner roller which is frictionally engaged with the input and output discs, a power outer roller which receives an axial load applied to the power inner roller from the input and output discs, a ball bearing which is operatively interposed between the power inner and outer rollers and a shaft which receives a radial load applied to the power inner roller from the input and output discs, a pair of trunnions rotatably supporting the power rollers respectively, each trunnion being connected to a transmission case in a manner to pivot about its pivot axis and having a power roller receiving recess for receiving therein corresponding one of the power rollers; and first roller bearings, each being operatively interposed between an inner wall of the power roller receiving recess of the trunnion and a back side of the power roller, so that the power roller is movable relative to the trunnion in a direction perpendicular to both a pivot axis of the trunnion and a rotation axis of the power roller, wherein the shaft is a one-body member comprises a first shaft portion on which the power outer roller is coaxially and tightly disposed and a second shaft portion on which the power inner roller is coaxially and rotatably disposed.
According to a second aspect of the present invention, there is provided a toroidal type continuously variable transmission which comprises input and output discs coaxially arranged; a pair of power rollers, each being operatively disposed between the input and output discs and including a power inner roller which is frictionally engaged with the input and output discs, a power outer roller which receives an axial load applied to the power inner roller from the input and output discs, a ball bearing which is operatively interposed between the power inner and outer rollers and a shaft which receives a radial load applied to the power inner roller from the input and output discs, a pair of trunnions rotatably supporting the power rollers respectively, each trunnion being connected to a transmission case in a manner to pivot about its pivot axis and having a power roller receiving recess for receiving therein corresponding one of the power rollers; and first roller bearings, each being operatively interposed between an inner wall of the power roller receiving recess of the trunnion and a back side of the power roller, so that the power roller is movable relative to the trunnion in a direction perpendicular to both a pivot axis of the trunnion and a rotation axis of the power roller, wherein the shaft is a one-body member comprises a first shaft portion on which the power outer roller is coaxially and tightly disposed and a second shaft portion on which the power inner roller is coaxially and rotatably disposed, wherein an inner wall of the power roller receiving recess is formed with inclined flat portions against which the first roller bearings abut, and wherein the power outer roller comprises a first surface formed with an annular guide groove which operatively receives the ball bearing, and a second surface formed with inclined flat portions which abut against the first roller bearings respectively.
According to a third aspect of the present invention, there is provided a toroidal type continuously variable transmission which comprises input and output discs coaxially arranged; a pair of power rollers, each being operatively disposed between the input and output discs and including a power inner roller which is frictionally engaged with the input and output discs, a power outer roller which receives an axial load applied to the power inner roller from the input and output discs, a ball bearing which is operatively interposed between the power inner and outer rollers and a shaft which receives a radial load applied to the power inner roller from the input and output discs, a pair of trunnions rotatably supporting the power rollers respectively, each trunnion being connected to a transmission case in a manner to pivot about its pivot axis and having a power roller receiving recess for receiving therein corresponding one of the power rollers; and first roller bearings, each being operatively interposed between an inner wall of the power roller receiving recess of the trunnion and a back side of the power roller, so that the power roller is movable relative to the trunnion in a direction perpendicular to both a pivot axis of the trunnion and a rotation axis of the power roller, wherein the shaft is a one-body member comprises a first shaft portion on which the power outer roller is coaxially and tightly disposed and a second shaft portion on which the power inner roller is coaxially and rotatably disposed, and wherein the first shaft portion is integrally formed with a flange portion which has a front flat surface which abuts against a rear flat surface of the power outer roller and a rear surface which is formed with inclined flat portions which abut against the first roller bearings respectively.